The so-called aiptasia-eating filefish (Acreichthys tomentosus) is an appropriately-named species with which every marine aquarist should be familiar. Why? “Because this fish is one of the best when it comes to the never-ending battle against aiptasia,” says Blue Zoo Aquatics Director of Marine Ornamental Research Mark Martin. “Not only does it love to eat aiptasia, but it is also generally considered reef compatible, and it’s far hardier than some of the other known aiptasia-eating fishes.”

Aiptasia, the pest anemone that can easily take over a saltwater tank and outcompete other ornamental invertebrates, is the bane of many a saltwater aquarist. While there are both mechanical and chemical means of battling aiptasia, a biological solution is best for a number of reasons. While there are other fishes, such as the copperband butterflyfish, which are known aiptasia-eaters, many of these fishes are not particularly hardy and may be difficult to wean onto a captive diet after the aiptasia is gone. Enter the aiptasia-eating filefish.

Also commonly known as the seagrass filefish, the bristle-tailed leatherjacket and the matted filefish, the aiptasia-eating filefish is a small (to 12 cm) species found throughout the Indo-West Pacific. Usually inhabiting seagrass beds and protected rubble zones and shallow reefs, this fish is considered common throughout its range. Anecdotally, the aiptasia-eating filefish is used as bait fish in some areas.

Although known for its prowess in the battle against pest anemones for quite some time, it has not been frequently imported for the marine aquarium trade. This is a shame given that it is a more reliable species than say a copperband butterflyfish when it comes to eating aiptasia, and it is far hardier in captivity. This fish is also considered reef-compatible (although individuals may nip at duncans, dendros, clams, and plate corals), and it readily accepts a captive diet (e.g., mysis shrimp).

The aiptasia-eating filefish should only be added to a peaceful community tank of 40 gallons or more.

“In short, this is great fish to add to a tank with an aiptasia infestation,” says Martin, “especially since it is behaviorally interesting and will continue to do well in your aquarium after the aiptasia is gone.”